Missing in action ... Mrs May got her nickname for disappearing when David Cameron needed her

The revelations come in a new book, Unleashing Demons, by Sir Craig Oliver who was Mr Cameron’s director of communications.

It also reveals how another pal of Mr Cameron questioned whether she was “an enemy agent” after he repeatedly begged her to “come off the fence” over the EU vote. The account by Sir Craig, who was appointed to Downing Street in 2011, reveals how Mrs May failed to back the PM on 13 separate occasions.

She eventually backed him but only after a desperate and “visibly wound-up” Mr Cameron phoned her to blast her position — but then “hung up” on her, pleased he had “made an impact on her”.

He made the call after hearing Mrs May was threatening to back Britain leaving the EU. Mr Oliver claims one of her excuses for not getting behind her boss was because she wanted a weekend away with her husband Philip.

Battle weary ... Mrs May and Philip Hammond “folded” over fighting for a better EU deal

Mrs May told him he shouldn’t argue for the “emergency brake” as it would not be approved by Germany.

The disclosure comes in All Out War by Sunday Times Political Editor Tim Shipman. He says Mrs May and then Foreign Secretary Philip Hammond “folded” over fighting for a better EU deal.

Aides revealed Mr Cameron looked “visibly deflated” when they wouldn’t support him and said, “if it wasn’t for my lily-livered Cabinet colleagues”.

Boris' 9 minute flip

BORIS Johnson told David Cameron Leave campaigners would be “crushed” in the EU referendum, it emerged last night.
But the now Foreign Secretary decided to be one of the faces of the Out campaign just nine minutes later.
BoJo’s final decision came just 24 hours after Mr Cameron thought he would “flipflop” and back the Government’s official position of remaining in the EU. The disclosure comes in the book by former Downing Street Communication chief Sir Craig Oliver. It also emerged that between messages saying he would back Leave, he revealed “depression is setting in”.
At this point, ex-PM Cameron believed “confused Inner” Johnson would join him and Chancellor George Osborne by backing the In campaign.
Oliver reveals in the book that BoJo’s attitude to Brexit was “cavalier and reckless” with the ultimate aim of helping his chances of reaching Number 10, echoing a claim by Foreign Minister Alan Duncan in a BBC documentary last week.